"Orbital Maneuvering System" redirects here, but can refer to any system used to modify a spacecraft's orbit.
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The Space Shuttle Orbital Maneuvering System (OMS), is a system of hypergolic liquid-propellant rocket engines used on the Space Shuttle. Designed and manufactured in the United States by Aerojet, the system was used during launch to produce supplementary thrust and on-orbit to provide orbital injection, orbital correction and the spacecraft's deorbit burn. The OMS consists of two pods mounted on the Orbiter's aft fuselage, on either side of the vertical stabilizer. Each pod contains a single AJ10-190 engine, based on the Apollo Service Module's Service Propulsion System engine, which produces 26.7 kilonewtons (Template:Convert/round lbf) of thrust with a specific impulse (Isp) of 316 seconds. Each engine could be reused for 100 missions and was capable of a total of 1,000 starts and 15 hours of burn time.
These pods also contained the Orbiter's aft set of reaction control system (RCS) engines, and so were referred to as OMS/RCS pods. The OM engine and RCS systems both burned monomethylhydrazine (MMH) as fuel, which was oxidized with dinitrogen tetroxide (N2O4), with the propellants being stored in tanks within the OMS/RCS pod, alongside other fuel and engine management systems. When full, the pods together carried around 8,174 kilograms (Template:Convert/round lb) of MMH and 13,486 kilograms (Template:Convert/round lb) of N2O4, allowing the OMS to produce a total of around 1,000 feet per second (Template:Convert/round m/s) of delta-v with a 65,000-pound (29,500 kg) payload.
An OMS pod detached from an Orbiter for maintenance